Railway car yokes serve the purpose of forming a pocket for the draft gear and maintaining the gear in proximity to the rear end of the coupler, so that forces applied to the coupler head are dampened by the gear. In standard freight car draft arrangements, a rectangular shaped block of steel is interposed between the butt of the coupler shank and the front working-end of the draft gear. This block extends crosswise through the front end of the yoke gear pocket and is termed the front follower. The relative positions of the front follower and draft gear to the coupler butt are maintained due to the securing of the yoke to the coupler shank by a connecting key, or pin.
The yoke design is predicated on the draft gear and coupler shank end. The yoke draft gear pocket may be compatible, in length, to the gear length and travel afforded by the gear. The shape of the front end of the yoke must be suited to receive the butt end of the coupler shank with proper provision for the connection of these two items. Thus, different yokes may be used to fit with different types of coupler shank butts.
During use, significant forces are applied to the yoke as the railway car is engaged and pulled along the track. These forces can cause bending stresses in various points of the yoke. Over time these bending stresses may cause the yoke to fail.